Junctions involving electrical wiring generally should be sealed or protected against exposure to the elements, particularly moisture: for inhibition of deterioration from corrosion; to reduce the likelihood of electrical shorts or the like; and, to otherwise enhance performance of the electrical system of concern. Generally, such junctions involve at least two, and often a large number, of insulated wires brought together, and exposed, at a particular junction. The junctions may be of a variety of types, including: connections having wires brought together from opposite directions, or a plurality of directions; pig-tail connections wherein the wires are generally directed toward the site of connection from a single direction; and, end or terminal connections, whereat a metal ring or the like, for attachment to a terminal, is mounted upon an end of a wire or plurality of wires. Generally maintenance of secure, conductive, connection at the point or points of engagement is facilitated through mechanical means such as by clamping and/or with use of welds or points of soldering.
As previously indicated, generally the connection involves exposure of conductive wire portions, from a plurality of extensions of insulated wire. The exposed portions, after the connection is made, should be protected from the environment, especially from moisture. Numerous seals and seal methods have been developed; however, none have been completely satisfactory for reasons discussed below. The conventional methods include the following:
An early, convenient and still frequently used method of providing a protective seal around a wire junction is through a wrapping of an insulating, typically treated-cotton, fabric, with an adhesive thereon, around the connection or junction. This method is inexpensive and easy to apply. However, it is not very effective in providing for a good moisture seal, as water can leak up along ends of the spirally-wrapped bundle. This is a particular problem if the connection involves at least two wires being brought together in a manner not co-axial, but rather generally parallel to, or adjacent, one another. For example, if two wires are brought to the connection from one direction and three wires are brought to the connection from an opposite direction, simply wrapping tape around the outside of the entire connection does not provide any moisture seal in the areas between adjacent insulated wires. For this reason insulating tape is, generally, considered an unacceptable manner of providing a good moisture seal on an electrical junction or the like.
A relatively recently developed alternative, to the use of tape, is the molding of a plug of vinyl or the like around the junction. To accomplish this, the junction, often involving multiple strands of wiring, is placed in a mold arrangement, and a vinyl plastic material or the like is injected into the mold and hardened therein to form a protective casing around the connection. This arrangement has not been completely acceptable for numerous reasons. First, injection molding has not been completely satisfactory in providing for seals when multiple wire arrangements are provided. That is, moisture leaking into spaces or areas between adjacent wires has still been a substantial problem. Secondly, when such vinyl molded arrangements are utilized under relatively high temperature conditions, such as are often found in automobile engine environments or the like, eventually deterioration of many conventional molded vinyl polymer materials occurs, in some instances resulting in a failure of the vinyl material, and loss of seal. This can occur, for example, should plasticizers be eventually leached from the seal.
Vinyl molded arrangements have been a particular problem when a wire or plurality of wires are brought into contact with, and attached to, a large metal connection, such as a mounting adaptor, ring terminal connector, or the like. In use, such metal connectors often expand and contract substantially, under wide temperature fluctuations. Molded vinyl seals, around such junctions, will tend to fracture in time, and fail, as the plasticizers are leached out and the metal continues to expand and contract, placing stress on the seal. Further, it is frequently difficult to obtain good vinyl insulator coverage of wire filaments at the point of connection to a terminal connector, or the like, when injection molding is relied on as the method of obtaining insulator placement. Also, vinyl molded arrangements do not generally bond and/or adhere well to typical wire insulators.
Yet another arrangement for providing an insulator around an electrical connection concerns the utilization of a heat shrinkable sleeve, tube or the like. For this method, an extension of heat shrink tubing is generally oriented over an otherwise exposed connection. The extension of tubing is then heat treated to shrink and seal around the connection. In some instances a hot-melt adhesive is used in association with heat shrink tubing; the hot-melt adhesive being oriented between the tubing and the wires, so that upon heating and shrinkage of the tubing the adhesive adheres the tubing to the wires.
Heat shrink tubing as been fairly effective in providing good moisture seals with small, simple, junctions; i.e. junctions or connections involving only a few wires, especially two co-axial wires. However, when three or more wires extend into the junction in a manner substantially parallel to one another, substantial problems with moisture leakage between adjacent wires still pervade. That is, heat shrink tubing, even when utilized in association with a hot-melt adhesive, does not provide good sealing between adjacent wires, particularly multiple, adjacent, substantially parallel, wires being brought into the junction.
Another problem with heat shrink tubing has been that it has not, in the past, been particularly effective over a very wide temperature range. Generally, for uses such as in the automotive industry, it is considered desirable that the seals exhibit effective performance over a temperature range of about -40.degree. C. to 130.degree. C. Over such a broad range, typical heat shrink tubing will sometimes fail, particularly at the lower temperatures. That is, the materials become inflexible and the seals are readily broken.
Another problem with heat shrink arrangements is that it is difficult to arrange such tubing to seal well when the connection involves a relatively large diameter bundle of wires on one side, and a relatively small diameter bundle of wires on the other side. That is, as the heat shrink material is shrunk, unless it is able to shrink a substantially constant amount over its entire length, which is often not possible when a large diameter and small diameter bundle of wires are located on opposite sides of the junction, maintenance of good seal is a problem. For example, typically heat shrink tubing will tend to slide toward the smaller diameter bundle or side, as it is shrunk. Thus, heat shrink seals do not work very effectively if, for example, one or two wires are brought into a connection from one direction but substantially more, such as three-to-five wires, are brought into the connection from an opposite direction. Further, heat shrink arrangements are not well-adapted for use on pig-tail splices or electrical connections involving mounting terminals.
In addition, it can be difficult to arrange heat shrink tubing over the connection of interest, especially since, generally, heat shrink tubing does not have a seam therein, and therefore must be slipped over the wires and then slid down the wires to cover the connection or junction of concern. Further, application of appropriate heat to cause shrinking may be energy intensive, inefficient and inconvenient.
A recently developed method and arrangement for providing seals around electrical connections involves the use of a plurality of vinyl strips sealed or molded together by ultrasonic welding techniques. Generally, for the conventional application of such a method, a vinyl strip is placed along each of opposite sides of an electrical junction The two strips are then molded to one another, in a manner sandwiching the junction therebetween, by means of ultrasonic welding or similar techniques.
Especially when multiple wire arrangements are utilized, such methods are not completely satisfactory for numerous reasons. First, as with all of the methods previously described, the method provides no effective seal to leakage of moisture between adjacent, substantially parallel, wires of multiple wire arrangements or bundles. Secondly, such arrangements inherently involve seams, along opposite sides where the vinyl strips are brought together. The seams may, in time, fail, especially under relatively high stress use conditions. Such arrangements have also been observed to be temperature sensitive, and thus are relatively likely to fail under high temperature or low temperature stress conditions. Finally, such vinyl strips do not generally provide any significant sealing interaction with the insulation material of most wires. That is, vinyl strips capable of being welded by ultrasonic methods generally do not form good seals with insulation materials typically utilized for wire insulation, for example the vinyl plastics such polyvinyl chloride plastics, cross-linked polyethylene materials, or the like.
What has been needed has been a method and arrangement for providing an effective moisture seal on or around an electrical junction, or the like. What has been particularly needed has been a method and arrangement particularly suited for providing a good effective positive seal for situations in which multiple wires, generally parallel or adjacent to one another, are brought into an electrical connection site or junction. Specifically, a method which has been especially needed is one which provides for an effective seal against moisture moving into the area of the junction by migration between adjacent insulated wires.